Build solid-solid interface without a vacuum layer

I am currently trying to build a solid-solid interface between two crystals using InterfaceBuilder. When I build this from any of the submodules within InterfaceBuilder (e.g. get_oriented_slabs then combine_slabs), I get the correct crystalline structures and interface, but there is a large vacuum layer that I don’t want. Are there parameters that I have to set correctly to not include the vacuum? Can I get rid of the vacuum layer afterwards or is there a different builder that I should be using?